U.S. Pat. No. 2,868,818 discloses the hydrochloride and hydrobromide salts of compounds having the general formulae: ##STR1## wherein R' is hydrogen, hydroxy, or an alkoxy or acyloxy group having a chain length of from one to four carbon atoms; R is hydroxy, or an alkoxy or acyloxy group having a chain length of from one to four carbon atoms; R.sup.2 is a hydroxy, amido, or a lower alkoxy group; and R.sup.3 and R.sup.4 are hydrogen, or lower alkyl or acyl.
The Merck Index, 8th Ed., Merck & Co., Inc., Rahway, N.J. (1968), at page 684 listed methyldopa hydrochloride.